Thiamin ingested in large amounts orally is not toxic, and usually the same is true of parenteral doses. Dietary intakes of thiamin up to 1,000 times the requirement are apparently safe for most animal species (NRC, 1987). The effects of excessive intakes of thiamin have not been studied in cats (NRC, 1987).
Lethal intravenous injections of thiamin administered to dogs have been reported to be 50 to 125 mg per kg (22.7 to 56.8 mg per lb) of body weight (Smith et al., 1947; 1948) and 350 mg per kg (159.1 mg per lb) of body weight (Gubler, 1991). Vasodilation, fall in blood pressure, bradycardia, respiratory arrhythmia and depression result when animals are given thiamin in large doses intravenously. In dogs, an oral dose of 100 to 115 µg of thiamin per kg (45.5 to 52.3 µg per lb) body weight per day appeared safe (Noel et al., 1971).
